Charge Compensation Layer Research Articles

A deep trench super-junction LDMOS with double charge compensation layer

A deep trench super-junction LDMOS with double charge compensation layer (DC DT SJ LDMOS) is proposed in this paper. Due to the capacitance effect of the deep trench which is known as silicon–insulator–silicon (SIS) capacitance, the charge balance in the super-junction region of the conventional deep trench SJ LDMOS (Con. DT SJ LDMOS) device will be broken, resulting in breakdown voltage (BV) of the device drops. DC DT SJ LDMOS solves the SIS capacitance effect by adding a vertical variable doped charge compensation layer and a triangular charge compensation layer inside the Con. DT SJ LDMOS device. Therefore, the drift region reaches an ideal charge balance state again. The electric field is optimized by double charge compensation and gate field plate so that the breakdown voltage of the proposed device is improved sharply, meanwhile the enlarged on-current region reduces its specific on-resistance. The simulation results show that compared with the Con. DT SJ LDMOS, the BV of the DC DT SJ LDMOS has been increased from 549.5 to 705.5 V, and the R on,sp decreased to 23.7 mΩ·cm2.

Highly Reliable Flexible Device with a Charge Compensation Layer.

Flexible devices fabricated with a polyimide (PI) substrate are essential for foldable, rollable, and stretchable products and various applications. However, inherent technical challenges remain in mobile charge-induced device instabilities and image retention, significantly hindering future technologies. Here, we introduce a new barrier material, SiCOH, into the backplane of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) and applied it to production-level flexible panels. We found that the SiCOH layer effectively compensates for the surface charging induced by fluorine ions at the interface between the PI substrate and the barrier layer under bias stress, thereby preventing abnormal positive shifts in threshold voltage (Vth) and image disturbance. The a-IGZO TFTs and metal-insulator-metal and metal-insulator-semiconductor capacitors with a SiCOH layer demonstrate reliable device performance, Vth shifts, and capacitance changes with an increase in gate bias stress. A flexible device with SiCOH enables the suppression of abnormal Vth shifts associated with PIs and plays a vital role in image sticking. This work provides new insights into process integrity and paves the way for expediting versatile form factors.

Improved Deep Trench Super-junction LDMOS Breakdown Voltage By Shielded Silicon-Insulator-Silicon Capacitor

Deep trench LDMOS is widely used in high-voltage level power devices. This paper proposes and optimizes a deep trench super-junction LDMOS with triangular charge compensation layer (TCCL DT SJ LDMOS), which solves the problem of charge imbalance in the super-junction region due to the Silicon-Insulator-Silicon (SIS) capacitance at both ends of the trench and improves the Breakdown Voltage (BV) of the device. This structure also helps to deplete the drift region at the bottom of the deep trench by adding P-buffer under the N-Pillars, which improves the doping concentration and reduces the specific on-resistance of the device. The simulation results show that compared with the Con. DT SJ LDMOS, the BV of the TCCL DT SJ LDMOS has been increased from 498V to 730V, and the power figure of merit (FOM) has increased by 12.8 MW / cm2(FOM = BV2 / Ron, sp).

A Lateral Double-Diffusion Metal Oxide Semiconductor Device with a Gradient Charge Compensation Layer

In order to better shield the substrate-assisted depletion (SAD) effect and improve the breakdown voltage of super-junction (SJ) devices, an SJ lateral double-diffusion metal oxide semiconductor device with a gradient charge compensation layer (gradient device) is proposed. The main feature of this structure is to introduce a gradient charge compensation layer between the SJ layer of a conventional device and the substrate. The depth of the gradient charge compensation layer increases gradually from the source to the drain. The charge distribution in the drift region is optimized by reducing the compensation charge on the side near the source and increasing the compensation charge on the side near the drain. Introduction of the layer improves shielding of the SAD effect, and the electric field on the surface of the structure is an approximately rectangular distribution, thus the breakdown voltage is improved. The simulation results show that the gradient device has 409-V breakdown voltage and a 9.5-MW cm−2 figure of merit with a drift region length of 21 μm. Compared with the conventional SJ structure (conventional device) with the same drift length, the breakdown voltage and figure of merit of the gradient device are increased by 57.3% and 137.5%, respectively.

PSJ LDMOS with a VK dielectric layer

A partial super junction lateral double-diffused metal–oxide–semiconductor field-effect transistor with a variable- k dielectric layer (PSJ VK LDMOS) is proposed in this Letter. Low- k material and PSJ are introduced into the device. PSJ provides a low-resistance channel to reduce the specific on-resistance ( R on,sp ). Furthermore, according to an enhanced dielectric layer field, low- k buried layer can sustain the high breakdown voltage (BV). To eliminate substrate-assisted depletion effect and improve the lateral BV of the proposed structure, the charge compensation layer in the device adopts a variation of lateral doping technique and is combined with the N pillar in PSJ. Ultimately, the simulation results show that BV of 795.5 V and the figure of merit (FOM) of 6.1 MW cm −2 are achieved for PSJ VK LDMOS. BV and FOM are enhanced by 71.4 and 81.1%, respectively, compared with con. PSJ SOI LDMOS with the drift region length of 46.5 μm. Furthermore, R on,sp of 103.4 mΩ cm 2 is reduced by 31.2% compared with the ‘silicon limit’ at the same BV class, which breaks the ‘silicon limit’.

High-Voltage Lateral Double-Diffused Metal-Oxide Semiconductor with Double Superjunction

A high-voltage lateral double-diffused metal-oxide semiconductor with double superjunction (DSJ LDMOS) is proposed in this paper. A vertical SJ under the drain and a lateral SJ in the drift region are introduced to form a double SJ in the DSJ LDMOS. To suppress the substrate-assisted depletion effect of the lateral SJ, a charge compensation layer linearly doped from source to drain is adopted in the drift region. In off-state, the vertical SJ enhances the depletion of the substrate to improve the vertical breakdown voltage (BV) and modulates the lateral electric field to increase the lateral BV. The lateral SJ increases the lateral BV and modulates the vertical electric field to improve the vertical BV. The vertical SJ is composed of N and P pillars with different concentrations. In on-state, the lateral SJ also provides a low-resistance channel, which decreases the specific on-resistance (Ron,sp). Simulation results indicate that the BV, figure of merit (FOM), and Ron,sp of the DSJ LDMOS are 1138 V, 10.5 MW cm−2, and 103.4 mΩ cm2, respectively. The BV and FOM of the DSJ LDMOS are increased by 31.3% and 483% compared with the conventional vertical SJ LDMOS (Con. VSJ LDMOS), while the Ron,sp of the DSJ LDMOS is reduced by 70%. The “silicon limit” is thus broken by the DSJ LDMOS.

Si/SiC heterojunction optically controlled transistor with charge compensation layer

A novel n-SiC/p-Si/n-Si optically controlled transistor with charge compensation layer has been studied in the paper. The performance of the device is simulated using Silvaco Atlas tools, which indicates excellent performances of the device in both blocking state and conducting state. The device also has a good switching characteristic with 0.54μs as rising time and 0.66μs as falling time. With the charge compensation layer, the breakdown voltage and the spectral response intensity of the device are improved by 90V and 33A/W respectively. Compared with optically controlled transistor without charge compensation layer, the n-SiC/p-Si/n-Si optically controlled transistor with charge compensation layer has a better performance.

High-pressure synthesis and crystal structures of the strontium oxogallates Sr2Ga2O5 and Sr5Ga6O14

High-pressure synthesis experiments in a piston–cylinder apparatus at 1.5GPa/3.0GPa and 1000°C resulted in the formation of single-crystals of Sr2Ga2O5 and Sr5Ga6O14, respectively. The structures of both compounds have been solved from single-crystal diffraction data sets using direct methods. The first compound is orthorhombic with space group type Pbca (a=10.0021(4)Å, b=9.601(4)Å, c=10.6700(4)Å, V=1024.6(4)Å3, Mr=394.68u, Z=8, Dx=5.12g/cm3) and belongs to the group of single layer gallates. Individual sheets are parallel to (001) and can be built from the condensation of unbranched vierer single chains running along [010]. The layers are characterized by the presence of four- and strongly elliptical eight-membered rings of corner connected tetrahedra in UUDD and UUUUDDDD conformation. Strontium atoms are sandwiched between the tetrahedral layers for charge compensation and are coordinated by six and seven oxygen ligands, respectively. Sr2Ga2O5 is isotypic with several other double sulfides and selenides. To the best of our knowledge, it is the first example of an oxide with this structure type. From a structural point of view, Sr5Ga6O14 is a phyllogallate as well. The crystal structure adopts the monoclinic space group P21/c (a=8.1426(3)Å, b=8.1803(3)Å, c=10.8755(4)Å, β=91.970(4)° V=723.98(5)Å3, Mr=1080.42u, Z=2, Dx=4.96g/cm3). Individual sheets extend along (001). Basic building units are unbranched dreier single chains parallel to [100]. The layers contain tertiary (Q3) und quaternary (Q4) connected [GaO4]-tetrahedra in the ratio 2:1 resulting in a Ga:O ratio of 3:7 and the formation of exclusively five-membered rings. Linkage between adjacent tetrahedral sheets is provided by three symmetrically independent strontium ions which are surrounded by six to eight oxygen atoms. The layers in Sr5Ga6O14 are similar to those observed in the melilite structure-type. Crystallochemical relationships between the present phases and other known compounds are discussed in detail.

The modification of ferroelectric LiNbO3(0001) surfaces using chromium oxide thin films.

The impact of ferroelectric polarization on the chemical and electronic properties of atomically thin layers of non-polar chromium oxide deposited on positively and negatively poled LiNbO3(0001) was studied. Chromium(III) oxide readily forms on LiNbO3; however, annealing at high temperatures was required to maintain well-ordered films as the thickness increased. Prolonged heating at these temperatures caused Cr diffusion into the LiNbO3 substrate. Comparing Cr 2p X-ray photoelectron spectroscopy (XPS) peak positions as a function of temperature and substrate polarization revealed no evidence of shifts from the peak positions expected for Cr2O3. The lack of any band offset between Cr2O3 on the oppositely poled surface suggests that charge compensation of the ferroelectric substrate occurs at least predominantly at the surface of the film, as opposed to the film-substrate interface. No evidence of shifts due to oxidation or reduction of the Cr was observed indicating that charge compensation did not involve a change in the ionic state of the Cr. Exposing the films to reactive oxygen species emitted from an oxygen plasma, however, caused a distinct high binding energy shoulder on the Cr 2p3/2 XPS peaks that could be associated with oxygen adsorption on surface Cr and concomitant oxidation to Cr(5+). This feature was used to gauge the concentration of O adatoms on the surfaces as a function of temperature for oppositely poled substrates; these measurements did not reveal any significant polarization dependence for oxygen desorption. Further, temperature programmed desorption measurements for a Cr2O3 film on α-Al2O3 showed a similar trend in O2 desorption. Therefore, it is concluded that the reactivity of Cr2O3 toward O is at least largely independent of substrate polarization despite data suggestive of charge compensation at the film surfaces.

Equivalent Substrate Model for Lateral Super Junction Device

The equivalent substrate (ES) model and the accordant optimized structure for the lateral super junction (LSJ) device are proposed in this paper. The ES, defined as the combination of the depleted substrate under the reverse voltage and the charge compensation layer (CCL) in the substrate, is treated as a whole to analyze the modulation impact of the compensation electric field ΔE on the total electric field of the LSJ. The analytical formulas for the surface electric field profiles of the LSJ are deduced from the 3-D Poisson equation and the Green function. The ES model reveals the essence and the suppression of the substrate-assisted depletion effect in the LSJ, from which the optimized substrate conditions are achieved. The optimized substrate condition allows the LSJ device featuring a similar breakdown voltage to that of the vertical super junction. Then four typical doping concentrations of the CCLs with four different compensation electric field strengths ΔEs are compared. The developed novel device with optimized CCL delivers a breakdown voltage of 301 V, realizing 157% improvement compared with the conventional LSJ with Ld=15 μm, which shows a superior performance to the LSJ devices reported. It is noteworthy that the ES model can also be used to analyze other LSJs.

Optical and Electrical Character of SICGe/SIC Heterojunction Phototransistor with Charge Compensation Layer

The optical properties of SiCGe epitaxial on 6H-SiC substrate by LPCVD were investigated by transmittance measurements. Swanepoel methods were used in order to calculate the optical properties of the sample. The result was use to simulation the performance of n-SiC/p-SiCGe/n-SiCGe heterojunction phototransistor with charge compensation layer. Simulation results show that with wide bandgap SiC emitter and p-type SiCGe charge-compensation layer, device responsivity doubled and breakdown voltage increased from 440V to 580V for the given structure

Evidence of Responsivity and Breakdown Voltage Improvement in SiCGe/SiC Phototransistor with Charge Compensation Layer

An n-SiC/p-SiCGe/n-SiCGe heterojunction phototransistor with charge compensation layer has been simulated with commercial simulator MEDICI. With wide bandgap SiC emitter and p-type SiCGe charge-compensation layer, device responsivity and breakdown voltage has been improved. It is found that with p-type SiCGe layer, the responsivity is nearly two times of without one. Furthermore, flat electrical field distribution during off-state enable it supports higher reverse bias, thus breakdown voltage increased from 450V to 580V for the given structure, and both breakdown voltage and responsivity increase with light absorption region length.

Switching Characters of SiCGe/SiC Heterojunction: An Optically Triggered Lateral Power Transistor with Charge Compensation Layer

The switching character of SiCGe/SiC heterojunction phototransistors with charge-compensation technique has been simulated with commercial simulator MEDICI. The influences of light power density, wavelength and carrier lifetime on switching characters were studied. Simulation result shown that the devices are latch-free device and fall time is much longer than rise time. The increasing of light power density and wavelength cause shorter rise time and longer fall time unless reaches SiCGe absorption edge 520nm, trade-off must made between responsivity and switching speed when carrier lifetime is considered, the ratio of them gets it maximum values at minority carrier lifetime equal 90ns.

New CMOS compatible super-junction LDMOST with n-type buried layer

A new super-junction lateral double diffused MOSFET (LDMOST) structure is designed with n-type charge compensation layer embedded in the p−-substrate near the drain to suppress substrate-assisted depletion effect that results from the compensating charges imbalance between the pillars in the n-type buried layer. A high electric field peak is introduced in the surface by the pn junction between the p−-substrate and n-type buried layer, which given rise to a more uniform surface electric field distribution by modulation effect. The effect of reduced bulk field (REBULF) is introduced to improve the vertical breakdown voltage by reducing the high bulk electric field around the drain. The new structure features high breakdown voltage, low on-resistance and charges balance in the drift region due to n-type buried layer.

Structural studies on Na 6Si 8O 19—a monophyllosilicate with a new type of layered silicate anion

The existence of a sodium silicate with composition Na 6Si 8O 19 has been known for more than forty years. However, until now the crystal structure of this phase was unknown. In the course of this work single crystals of the Na 6Si 8O 19 have been prepared from the devitrification of a glass at ambient pressure. The title compound is monoclinic, space group P 12 1 / c 1 with Z = 4 and pseudo-orthorhombic unit-cell parameters: a = 4.9038 ( 5 ) Å , b = 23.481 ( 3 ) Å , c = 15.392 ( 2 ) Å , β = 90.14 ( 1 ) ° and V = 1772.3 ( 4 ) Å 3 . The structure has been solved by direct methods and refined to a residual of R ( | F | ) = 0.064 for 2327 independent observed reflections. Furthermore, micro-Raman spectra have been obtained from single crystal grains. Na 6Si 8O 19 belongs to the group of phyllosilicates and is based on layers of tetrahedra parallel to ( 001 ) . Individual sheets can be described as being built by the condensation of four different zweier single chains of SiO 4-tetrahedra running parallel to the a-axis. Due to the specific linkage of the chains the single silicate layers consist of both threefold and fourfold connected tetrahedra in the ratio Q 3 : Q 4 = 3 : 1 . Stacking of the layers along to the c-axis results in a three dimensional structure in which the sodium cations reside on six crystallographically independent sites between the layers for charge compensation. They are coordinated by 5–6 oxygen ligands forming distorted trigonal bipyramids and octahedra, respectively.

High pressure mixed alkali disilicates in the system Na2— xKxSi2O5: hydrothermal synthesis and crystal structures of NaKSi2O5-II and Na0.67K1.33Si2O5

Abstract Single crystal growth experiments for NaKSi2O5 and Na0.67K1.33Si2O5 have been successfully performed by hydrothermal crystallization of two glasses at 500°C and 1 kbar during 24 hours. For a glass with a Na : K ratio of 1 : 1 a previously unknown NaKSi2O5 modification named phase II was obtained. The structure of NaKSi2O5-II has been solved from a single crystal diffraction data set and refined to a residual of R(|F|)= 0.032 for 1186 independent reflections. The compound is monoclinic with space group P21/c (a = 4.852(1) Å, b = 13.594(2) Å, c = 7.463(1) Å, β = 91.20(2)° V = 492.1(2) Å3, Mr = 198.27 u, Z = 4, Dx = 2.68 g/cm3, μ(MoKα ) = 1.58 mm–1) and belongs to the group of double chain silicates. Individual double chains can be described as being built by the condensation of zweier single chains of SiO4-tetrahedra running parallel to the a-axis. Each chain contains four-membered rings. Alkali-atoms are 6- and 8-fold coordinated by the oxygen ligands. NaKSi2O5-II is isotypic with the structure of NaRbSi2O5 which has been synthesized at room-pressure. Hydrothermal treatment of a second glass with composition Na0.5K1.5Si2O5 resulted in the formation of single-crystalline material of Na0.67K1.33Si2O5, slightly Na-richer than the starting composition. The platy crystals showed twinning by pseudo-merohedry, a feature we took account of by separating the reflections from the different twin individuals during the data collection. Structure solution has been accomplished by direct methods. The subsequent refinement converged to a residual of R(|F|) = 0.037 for 1543 independent reflections. The compound is mono clinic as well with space group I2/a (a = 12.731(2) Å, b = 7.321(1) Å, c = 17.827(3) Å, β = 100.85(2)° V = 1631.9(6) Å3, Mr = 206.32 u, Z = 12, Dx = 2.53 g/cm3, μ(MoKα ) = 1.78 mm–1) and belongs to the group of single layer silicates. A single layer consists of four-, six- and eight-membered rings, which are parallel to (100), and can be described as being built by the condensation of unbranched dreier single chains running along the b-axis. The stacking of the layers results in a three-dimensional structure in which the alkali cations reside between the layers for charge compensation. The distribution of the alkali atoms among the three crystallographically different positions M(1), M(2) and M(3) shows a definite preference of the larger potassium for the M(1) and M(2) site; the M(3) site is K-free. The alkali-atoms are 5- and 6- fold coordinated by the oxygen atoms. The geometrical and topological features of the single tetrahedral sheets in Na0.67K1.33Si2O5 are very similar to those observed in the phase I of NaKSi2O5. Differences can be attributed to different ways of stacking of adjacent sheets, and different sequences of up and down pointing tetrahedra within the rings.

Hydrothermal synthesis and structural characterization of κ-Na 2Si 2O 5 and Na 1.84K 0.16Si 2O 5

Single crystals of a new sodium disilicate modification labeled κ-Na 2Si 2O 5 have been prepared from the hydrothermal crystallization of a glass at 700 °C and 3 kbar. The structure has been solved and refined to a residual of R(| F|)=0.035 for 750 independent observed reflections. The compound is orthorhombic with space group Pn2 1 a ( a=8.128(1) Å, b=4.8322(8) Å, c=11.977(3) Å, V=470.4(3) Å 3, Z=4, D x =2.57 g/cm 3, μ( Mo K α)=0.87 mm −1) and belongs to the group of single layer silicates. Individual sheets can be described as being built by the condensation of zweier single chains of SiO 4-tetrahedra parallel to the b-axis or, alternatively, by condensation of vierer single chains parallel to the a-axis. The layers contain six-membered rings in UDUDUD conformation. The stacking of the layers parallel to the c-axis results in a three-dimensional structure in which the alkali cations reside on two crystallographically independent sites (M(1) and M(2)) between the layers for charge compensation. The geometrical and topological features of the single tetrahedral sheets in κ-Na 2Si 2O 5 are almost identical to those observed in β- and C-Na 2Si 2O 5. Differences between the structures can be attributed to different ways of stacking of adjacent sheets and are discussed in detail. Small amounts of potassium can be substituted for sodium without changing the structure type. At slightly different synthesis conditions (600 °C, 1 kbar) we obtained an isostructural mixed alkali disilicate with composition Na 1.84K 0.16Si 2O 5 ( a=8.172(2) Å, b=4.849(1) Å, c=12.078(3) Å, V=478.6(3) Å 3). The distribution of the alkali atoms among the two M(1) and M(2) positions shows a definite preference of the larger potassium for the M(1) site; the M(2) site is K-free.

The crystal structure of a mixed alkali phyllosilicate with composition Na1.55K0.45Si2O5

The crystal structure of Na 1.55 K 0.45 Si 2 O 5 has been solved and refined to a final residual R 1 of 0.048 for 1208 independent reflections. The compound is monoclinic with space group P 2 1 /c ( a = 4.845(1) A, b = 8.647(2) A, c = 11.992(3) A, β = 90.31(4)°, V = 503.1(4) A 3 , M r = 189.40 u , Z = 4,λ(Mo K α ) = 0.71073 A, D x = 2.51 g/cm 3 , μ(Mo K α ) = 1.14 mm −1 ). The crystal showed twinning by pseudo-merohedry according to 2 [100] , a feature which was accounted for in the refinements. The compound belongs to the group of single-layer silicates. Individual sheets can be described as being built by the condensation of Zweier single chains of SiO 4 tetrahedra parallel to the a axis or, alternatively, by condensation of Vierer single chains parallel to the b axis. The layers contain six-membered rings in UUDUUD or DDUDDU conformation. The stacking of the layers parallel to the c axis results in a three-dimensional structure in which the alkali cations reside between the layers for charge compensation. The distribution of the alkali atoms among the two crystallographically different M(1) and M(2) positions shows a definite preference by the larger potassium for the M(1) site. The smaller M(2) site is K-free.

The Crystal Structure of δ-Na2Si2O5

The crystal structure of δ-Na2Si2O5 has been solved and refined to an R index of 0.053 for 933 independent reflections. The compound is monoclinic with space group P21/n (a=8.393(2) Å, b=12.083(3) Å, c=4.843(1) Å, β=90.37(3)°, V=491.1(1) Å3, Mr=182.15 u, Z=4, λ(MoKα)=0.71073 Å, Dx=2.46 g/cm3, μ(MoKα)=8.3 cm−1). The crystal showed twinning by pseudo-merohedry according to 2100, a feature which we took account of in the refinements. The compound belongs to the group of single layer silicates. Individual sheets can be described as being built by the condensation of zweier single chains of SiO4 tetrahedra parallel to the c-axis or, alternatively, by condensation of vierer single chains parallel to the a-axis. The stacking of the layers parallel to the b-axis results in a three-dimensional structure in which the sodium cations reside between the layers for charge compensation.